Many electronic digital printers apply print characters to paper via multiple exposure elements of an exposure device. In some printers, such as the NexPress 2100 from NexPress Solutions LLC, the exposure elements are light emitting diodes (“LEDs”) and the exposure device is an LED printhead.
The LEDs are typically controlled by a printhead driver integrated circuit (“IC”). Each driver IC may control many LEDs, and a printer may include multiple driver ICs.
Known LED printhead assemblies and other types of printheads typically having a “fixed width” architecture, meaning that a unique substrate assembly is designed to match the product exposure width requirements. With the known printheads, for every line of exposure, all of the LED driver ICs populated on the substrate must be reloaded for every line of exposure. Specifically, the data register for each LED element must be resent data for each and every line of exposure. Intended “off” LEDs must be loaded with a zero data value for each line. In many applications, certain LEDs at the ends of an LED printhead are not used and must be continually loaded with zero data. This redundant operation to load unused LEDs with zero data wastes a significant amount of data loading bandwidth and therefore limits the speed of the printing device.
Since known LED printheads are a fixed width they tend to be used for specific products. It is not practical to use a wider LED printhead for narrower product applications due to-unnecessary data loading and bandwidth loss.
Fixed width does not allow for running a reduced image area at a higher speed without increasing the data rate of flow. Known LED image path driving systems can easily be adapted to a change in the amount of data sent, but cannot easily increase the speed at which the data is sent.
FIG. 1 is a block diagram of a prior art fixed width printhead. Printhead 10 is formed from a string of LEDs 18. Printhead 10 has a fixed width 12 based on the entire string of LEDs 18. For an image area requirement 14, some of the LEDs form unused areas 16 and 17. However, unused areas 16, 17 still must be loaded with zero data for each and every line of exposure. As discussed, this reduces the speed of the printing device.
Based on the foregoing, there is a need for a flexible printhead in which unused portions can be turned off or disabled.